1. Field of the Invention
The invention relates to pyrrole-containing peptidomimetic compounds that inhibit the enzymatic activity of picornaviral 3C proteases, especially rhinovirus 3C proteases (RVPs), and that retard viral growth in cell culture. The invention also relates to the use of these compounds in pharmaceutical compositions, methods of treatment of rhinoviral infections using these compounds and compositions, and processes for the synthesis of these compounds and compounds useful in the syntheses thereof.
2. Related Background Art
The picornaviruses are a family of tiny non-enveloped positive-stranded RNA-containing viruses that infect humans and other animals. These viruses include the human rhinoviruses, human polioviruses, human coxsackieviruses, human echoviruses, human and bovine enteroviruses, encephalomyocarditis viruses, meningitis virus, foot and mouth viruses, hepatitis A virus, and others. The human rhinoviruses are a major cause of the common cold. To date, there are no effective therapies on the market that cure the common cold, only treatments that relieve the symptoms.
Picornaviral infections may be treated by inhibiting the proteolytic picornaviral 3C enzymes. These enzymes are required for the natural maturation of the picornaviruses. They are responsible for the autocatalytic cleavage of the genomic, large polyprotein into the essential viral proteins. Members of the 3C protease family are cysteine proteases, where the sulfhydryl group most often cleaves the glutamine-glycine amide bond. Inhibition of 3C proteases is believed to block proteolytic cleavage of the viral polyprotein, which in turn can retard the maturation and replication of the viruses by interfering with viral particle production. Therefore, inhibiting the processing of this cysteine protease with selective small molecules that are specifically recognized should represent an important and useful approach to treat and cure viral infections of this nature and, in particular, the common cold.
Some small-molecule inhibitors of the enzymatic activity of picornaviral 3C proteases (i.e., antipicornaviral compounds) have been recently discovered. See, for example: U.S. Pat. No. 5,856,530; U.S. Pat. No. 5,962,487; U.S. Pat. No. 6,020,371; and U.S. patent application Ser. No. 09/301,977, filed Apr. 29, 1999, by Dragovich et al. See also: Dragovich et al., “Structure-Based Design, Synthesis, and Biological Evaluation of Irreversible Human Rhinovirus 3C Protease Inhibitors . . . ,” J. Med. Chem. (1999), Vol. 42, No. 7, 1203-1212, 1213-1224; and Dragovich et al., “Solid-phase Synthesis of Irreversible Human Rhinovirus 3C Protease Inhibitors . . . ,” Bioorg. & Med. Chem. (1999), Vol. 7, 589-598. There remains a desire, to discover small-molecule compounds that are especially potent antipicornaviral agents.
Inhibitors of other related cysteine proteases such as cathepsins have been described in, e.g., U.S. Pat. No. 5,374,623; U.S. Pat. No. 5,498,616; and WIPO International Publication Nos. WO 94/04172, WO 95/15749, WO 97/19231, and WO 97/49668. There yet remains a need for inhibitors targeting the picornaviral 3C cysteine protease with desirable pharmaceutical properties, such as high specificity, good therapeutic index or low toxicity.